Tangential cutting insert and milling cutter

ABSTRACT

A tangential cutting insert having two identical opposing end surfaces with two identical opposing major side surfaces and two identical opposing minor side surfaces extending between them. Each end surface has a peripheral edge containing cutting edges and four corners of which two are lowered and two are raised. Each end surface is provided with at least one projecting abutment member having a projecting abutment surface, wherein in a side view of either major side surface, the at least one projecting abutment surface is concave.

RELATED APPLICATIONS

This is a Continuation of U.S. patent application Ser. No. 10/454,078,filed Jun. 4, 2003, now U.S. Pat. No. ______.

FIELD OF THE INVENTION

The present invention relates to a tangential indexable cutting insertand a milling cutter for use in metal cutting processes in general andfor milling a square shoulder in a workpiece in particular.

BACKGROUND OF THE INVENTION

Tangential cutting inserts, also known as on-edge, or lay down, cuttinginserts, are oriented in an insert holder in such a manner that during acutting operation on a workpiece the cutting forces are directed along amajor (thicker) dimension of the cutting insert. An advantage of such anarrangement being that the cutting insert can withstand greater cuttingforces than when oriented in such a manner that the cutting forces aredirected along a minor (thinner) dimension of the cutting insert.

There is disclosed in EP 0 769 341 a face milling cutter employing adouble-sided indexable tangential cutting insert having a prismoidalshape with two opposed generally rectangular rake surfaces connected byside surfaces. The cutting insert has a basic “negative” geometry andtherefore in order to provide the necessary clearance between thecutting insert and the workpiece, when mounted in a face-mill, thecutting insert is oriented with a negative axial rake angle. However,negative axial rake angles are disadvantageous, e.g., they have beenfound to be deficient in cutting efficiency for applications involvingdifficult to machine materials.

There is disclosed in WO 96/35536 a double-sided indexable tangentialcutting insert which when mounted in a face-mill has a positive axialrake angle, even when the necessary clearance between the cutting insertand the workpiece is provided. This cutting inserts presents twoperipheral cutting edges for a right-hand face mill and two peripheralcutting edges for a left-hand face mill.

A double-sided indexable tangential cutting insert for a boring toolhead is disclosed in U.S. Pat. No. 5,333,972. The insert is provided ateach end with a protruding flat island. Each long cutting edge isinclined at an angle of 3° relative to the protruding flat island,defining an “insert axial rake angle”. Rearward of each cutting edge isa descending land surface that merges with an increasing incident anglesurface to form a chip breaker groove. Each increasing incident anglesurface extends from its associated descending land surface to anadjacent island, at either the top or the bottom of the cutting insert.The cutting insert is left or right handed. It is manufactured to beright-handed and, when flipped around, is left-handed. It will beappreciated that the magnitude of the insert axial rake angle is limitedfor practical reasons. Any increase in the insert axial rake angle willresult in an increase in the “vertical” extent of the increasingincident angle surface (see FIG. 3 of U.S. Pat. No. 5,333,972) that willhave an adverse effect on chip development and evacuation.

It is an object of the present invention to provide a double-sidedindexable tangential cutting insert that substantially overcomes theabove-mentioned problems.

It is a further object of the present invention to provide adouble-sided indexable tangential cutting insert having four maincutting edges, for a given direction of rotation of the milling cutter,each main cutting edge having a positive axial rake angle when mountedas an operative cutting edge in a milling cutter.

It is yet a further object of the present invention to provide adouble-sided indexable tangential cutting insert capable of milling asquare shoulder in a workpiece.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a tangentialcutting insert, for use in a milling cutter The tangential cuttinginsert includes:

two identical opposing end surfaces, each end surface having fourcorners including two lowered corners and two raised corners, thelowered corners being closer to a median plane M than the raisedcorners, each end surface being provided with at least one abutmentmember having an abutment surface;

a peripheral side surface extending between the two opposing endsurfaces and comprising two identical opposing major side surfaces andtwo identical opposing minor side surfaces; and

a peripheral edge formed at the intersection of each end surface and theperipheral side surface, at least two sections of each peripheral edgeconstituting cutting edges,

wherein in a side view of either major side surface, the abutmentsurface lies on a concave surface.

In a preferred embodiment, the two identical opposing end surfaces have180° rotational symmetry about a first axis A1 passing therethrough, thetwo identical opposing major side surfaces have 180° rotational symmetryabout a second axis A2 passing therethrough, the second axis A2 beingperpendicular to the first axis A1, and a minor plane P1 is defined bythe first axis A1 and the second axis A2; the two identical opposingminor side surfaces have 180° rotational symmetry about a third axis A3passing therethrough, the third axis A3 being perpendicular to the firstaxis A1 and the second axis A2, and a major plane P2 is defined by thefirst axis A1 and the third axis A3; the median plane M is defined bythe second axis A2 and the third axis A3; and the at least one abutmentmember comprises a projecting abutment surface.

Preferably, in a side view of either major side surface, the abutmentsurface is generally V-shaped.

In accordance with an embodiment of the present invention, in anend-view of the cutting insert, the abutment surface is generallyrectangular in shape having two parallel long edges extending betweentwo short edges, the long edges making an angle of β with the majorplane P2.

In accordance with a specific application of the first embodiment, β=2°.

If desired, the abutment surface comprises three flat portions, twoouter flat portions with an inner flat portion therebetween, each outerflat portion extending from a respective short edge to the inner flatportion.

In accordance with a first embodiment of the present invention, in anend-view of the cutting insert two median lines are defined, one foreach outer flat portion, the median lines do not overlap and do not lieon a common straight line.

Preferably, the two median lines are parallel.

Further preferably, the two median lines are parallel to the major sidesurfaces.

In accordance with a second embodiment of the present invention, in anend view of the cutting insert the at least one abutment member has anelongated S-shape.

In accordance with a third embodiment of the present invention, each endsurface is provided with two abutment members.

Preferably, the two abutment members are located on opposite sides ofthe minor plane P1.

Further preferably, a major portion of a first of the two abutmentmembers is located on a first side of the major plane P2 and a majorportion of a second of the two abutment members is located on a secondside of the major plane P2.

If desired, each minor side surface is divided into two minor sidesub-surfaces by the major plane along a join where the major planeintersects the minor side surface, each minor side sub-surface extendingaway from the join at an angle α with respect to a plane passing throughthe join and parallel to the minor plane P1.

In accordance with the present invention, each minor side surface mergeswith an adjacent major side surface at a corner side surface, whereineach corner side surface extends between a given raised corner of one ofthe two opposing end surfaces and a given lowered corner of the other ofone of the two opposing end surfaces.

In accordance with the present invention, each cutting edge comprises amajor cutting edge, a minor cutting edge and a corner cutting edge,therebetween.

In accordance with the present invention, major, corner, and minor edgesare formed at the intersection of the major, corner and minor sidesurfaces, respectively with an adjacent end surface.

In accordance with the present invention, each corner cutting edge isassociated with a given raised corner.

Generally, each major cutting edge extends along substantially the wholelength of an associated major edge.

Generally, each minor cutting edge extends along at least half of thelength of an associated minor edge.

In accordance with the present invention, the cutting insert furthercomprises an insert through bore extending between the major sidesurfaces and having a bore axis B coinciding with the second axis A2.

Generally, a first major dimension D1, measured between the endsurfaces, is greater than a minor dimension D2 measured between themajor side surfaces.

Further generally, a second major dimension D3, measured between theminor side surfaces, is greater than the minor dimension D2.

There is also provided in accordance with the present invention, amilling cutter including at least one cutting insert as described above,and a cutter body having at least one insert pocket in which the atleast one cutting insert is retained, the at least one insert pocketcomprising adjacent side and rear walls generally transverse to a base,the rear wall being generally convex; the side wall being provided withan axial location surface that abuts a given minor side surface of theat least one cutting insert at a given axial abutment region; the rearwall being provided with two tangential location surfaces, located oneither side of a central region of the rear wall, a first of the twotangential location surfaces abuts a first tangential abutment surfacelocated on the at least one cutting insert, a second of the twotangential location surfaces abuts a second tangential abutment surfacelocated on the at least one cutting insert.

In accordance with the present invention, the given axial abutmentregion is located on a forward region of a radially outer minor sidesub-surface, the forward region being distal the rear wall of the insertpocket.

Further in accordance with the present invention, the lower and uppertangential abutment surfaces are located on opposite sides of the minorplane P1.

In accordance with the first and second embodiments, each end surface ofthe at least one cutting insert is provided with one abutment member andthe first and second tangential abutment surfaces are located on the oneabutment member.

In accordance with the third embodiment, each end surface of the atleast one cutting insert is provided with two abutment member and thefirst tangential abutment surface is located on one of the two abutmentmembers, and the second tangential abutment surfaces is located on theother one of the abutment member.

In another aspect, the present invention is directed to a tangentialcutting insert comprising two identical opposing end surfaces, each endsurface having four corners including two lowered corners and two raisedcorners, the lowered corners being closer to a median plane M than theraised corners, each end surface being provided with two abutmentmembers separated by a central recessed region, each abutment memberhaving an abutment surface. The insert also has a peripheral sidesurface extending between the two opposing end surfaces and comprisingtwo identical opposing major side surfaces and two identical opposingminor side surfaces. A peripheral edge is formed at the intersection ofeach end surface and the peripheral side surface, at least two sectionsof each peripheral edge constituting cutting edges. In a side view ofeither major side surface, the abutment surfaces of each abutment memberof a given end surface lie on a concave surface.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding, the invention will now be described, by wayof example only, with reference to the accompanying drawings in which:

FIG. 1 is a perspective view of a cutting insert in accordance with afirst embodiment of the present invention;

FIG. 2 is a first side view of the cutting insert in FIG. 1;

FIG. 3 is an end view of the cutting insert shown in FIG. 1;

FIG. 4 is a second side view of the cutting insert shown in FIG. 1;

FIG. 5 is a cross-sectional view of the cutting insert shown in FIG. 1taken along the line V-V in FIG. 4;

FIG. 5 is a cross-sectional view of the cutting insert shown in FIG. 1taken along the line V-V in FIG. 4;

FIG. 6A is an enlarged scale partial cross section of the cutting insertshown in FIG. 1 taken along the line VIA-VIA in FIG. 3;

FIG. 6B is an enlarged scale partial cross section of the cutting insertshown in FIG. 1 taken along the line VIB-VIB in FIG. 3;

FIG. 6C is an enlarged scale partial cross section of the cutting insertshown in FIG. 1 taken along the line VIC-VIC in FIG. 3;

FIG. 7 is a perspective view of the cutting insert in accordance withthe present invention with a ground primary relief surface;

FIG. 8 is a perspective view of a milling cutter in accordance with thepresent invention;

FIG. 9 is a perspective view of a portion of the cutter body of themilling cutter in accordance with the present invention, showing indetail an insert pocket;

FIG. 10 is an end view of a cutting insert in accordance with a secondembodiment of the present invention;

FIG. 11 is a side view of a cutting insert in accordance with the secondembodiment of the present invention;

FIG. 12A is an enlarged scale partial cross section of the cuttinginsert in accordance with the second embodiment taken along the lineXIIA-XIIA in FIG. 10;

FIG. 12B is an enlarged scale partial cross section of the cuttinginsert in accordance with the second embodiment taken along the lineXIIB-XIIB in FIG. 10;

FIG. 12C is an enlarged scale partial cross section of the cuttinginsert in accordance with the second embodiment taken along the lineXIIB-XIIB in FIG. 10;

FIG. 13 is a perspective view of a cutting insert in accordance with athird embodiment of the present invention;

FIG. 14 is a side view of the cutting insert shown in FIG. 13;

FIG. 15 is an end view of the cutting insert shown in FIG. 13;

FIG. 16A is an enlarged scale partial cross section of the cuttinginsert shown in FIG. 13 taken along the line XVIA-XVIA in FIG. 15;

FIG. 16B is an enlarged scale partial cross section of the cuttinginsert shown in FIG. 13 taken along the line XVIB-XVIB in FIG. 15; and

FIG. 16C is an enlarged scale partial cross section of the cuttinginsert shown in FIG. 13 taken along the line XVIC-XVIC in FIG. 15.

DETAILED DESCRIPTION OF THE INVENTION

Attention is first drawn to FIGS. 1 to 6C, showing a cutting insert 10in accordance with a first embodiment of the present invention. Thecutting insert 10 is tangential and indexable. The cutting insert 10 istypically manufactured by form-pressing and sintering carbide powders.The cutting insert 10 is generally rectangular in an end view and hastwo identical opposing end surfaces 12. Each end surface 12 has 180°rotational symmetry about a first axis A1 passing through the two endsurfaces 12.

A peripheral side surface 14 extends between the two opposing endsurfaces 12 and comprises two opposed identical minor side surfaces 16,two opposed identical major side surfaces 18, and four opposed cornerside surfaces 22. Adjacent minor and major side surfaces 16, 18 merge ata common corner side surface 22. The two identical opposing major sidesurfaces 18 each have 180° rotational symmetry about a second axis A2passing through the opposing major side surfaces 18. The second axis A2is perpendicular to the first axis A1. Similarly, the two identicalopposing minor side surfaces 16 each have 180° rotational symmetry abouta third axis A3 passing through the opposing minor side surfaces 16. Thethird axis A3 is perpendicular to the first axis A1 and to the secondaxis A2. A minor plane P1 defined by the first axis A1 and the secondaxis A2, a major plane P2 defined by the first axis A1 and the thirdaxis A3 and a median plane M is defined by the second axis A2 and thethird axis A3.

Each end surface 12 has four corners, two lowered corners 26 and tworaised corners 24. The lowered corners 26 being closer to the medianplane M than the raised corners 24. Each corner side surface 22 extendsbetween a given raised corner 24 of one of the two opposing end surfaces12 and a given lowered corner 26 of the other of one of the two opposingend surfaces 12. Each end surface 12 is provided with a projectingabutment member 28 having a projecting abutment surface 30, wherein in aside view of either major side surface 18, the projecting abutmentmember 28 is generally concave in form. The projecting abutment surface30 comprises three generally flat portions, two outer portions 32 withan inner portion 34 therebetween. Therefore, in a side view of eithermajor side surface 18, each projecting abutment surface 30 lies on aconcave surface S which is generally V-shaped in form.

Referring to FIG. 3, it can be seen that in an end-view of the cuttinginsert 10 the projecting abutment surface 30 is generally rectangular inshape having two parallel long edges 36 extending between two shortedges 38. Therefore, each outer flat portion 32 of the projectingabutment surface 30, extends from a respective short edge 38 to theinner flat portion 34.

A peripheral edge 40 is formed at the intersection of each end surface12 and the peripheral side surface 14. For each end surface 12, theperipheral edge 40 comprises two major edges 42, formed by theintersection of the major side surfaces 18 with the end surface 12; twominor edges 44, formed by the intersection of the minor side surfaces 16with the end surface 12; and two corner edges 42, formed by theintersection of the corner side surfaces 22 with the end surface 12.

At least two sections of each peripheral edge 40 the cutting insert 10constitute cutting edges 52. Each cutting edge 52 comprises a majorcutting edge 54, extending along substantially the whole length of itsassociated major edge 42; a minor cutting edge 56, extending along atleast half of the length of its associated minor edge 44; and a cornercutting edge 58, associated with a raised corner 24 and at which themajor and minor cutting edges 54, 56 merge. Adjacent each cutting edge52 in the end surfaces 12 is a rake surface 60 along which chips,removed from a workpiece during a milling operation, flow. Between therake surface 60 and the projecting abutment member 28 there is a chipgroove 62. The portion of the projecting abutment member 28 adjacent thechip forming groove 62 constitutes a chip deflector 64.

Referring to FIG. 3, it is seen that each minor side surface 16 isdivided into two minor side sub-surfaces 70 by a join 72 where the majorplane P2 intersects the minor side surface 16. Each minor sidesub-surface 70 extends away from the join 72 at an angle α with respectto a plane P3 passing through the join 72 and parallel to the minorplane P1. In accordance with a specific application this angle isapproximately 1.5°. The cutting insert is provided with a through bore74 extending between the major side surfaces 18 and having a bore axis Bcoinciding with the second axis A2.

As will become apparent below, with reference to the milling cutter inaccordance with the present invention, the section of the major cuttingedge 54 adjacent the raised corner 24 constitutes a leading end 66 ofthe major cutting edge 54 whereas, the section of the major cutting edge54 adjacent the lowered corner 26 constitutes a trailing end 68 of themajor cutting edge 54. As can be seen in FIG. 4, in a side view of thecutting insert 10, the projecting abutment member 28 in the region ofthe leading end of the major cutting edge 54 and up to and a littlebeyond the region of the minor plane P1, does not protrude by much abovethe major cutting edge 54. As a consequence, chips in this region arecompletely formed during a milling process. However, in the region ofthe trailing end 68 of the major cutting edge 54, the chip deflector 64protrudes much further than it does in the region of the leading end 66,which can disturb the development of the chips. In order to reduce theinfluence of the protruding chip deflector 64 in the region of thetrailing end 68, the chip deflector 64 is designed to be more distantfrom the major cutting edge 54 in the region of the trailing end 68 thanit is in the region of the leading end 66. Consequently, as can be seenin FIG. 3, in an end-view of the cutting insert 10 in accordance withthe first embodiment of the present invention the long edges 36 of theprojecting abutment member 28 are oriented at a small angle β withrespect, to the major plane P2. In accordance with a specificapplication this angle is 2°. Although the shape of the major cuttingedge 54 is shown in FIG. 4 to be generally straight in a side view,apart from section adjacent the trailing end 68, the major cutting edge54 can have any desired shape. Further with reference to FIG. 4, it canbe seen that in a side view of the major side surface 18, the majorcutting edge 54 generally slopes downwardly from the raised corner 24 tothe lowered corner 26. With reference to FIG. 2, it can be seen that ina side view of the minor side surface 16, the minor edge 44 is clearlydivided into two sections, a first section 46 extending from the raisedcorner 24 to approximately the major plane P2 and a second section 48extending from the major plane to the lowered corner 26. The firstsection 46 is approximately straight and is perpendicular to the majorside surface 18 in a side view, see FIG. 2, and is oriented at the angleα with respect to a plane P3 in an end view, see FIG. 3. The secondsection 48 extends from approximately the major plane P2 slopinglytowards the lowered corner 26 in an end view, see FIG. 2, and isoriented at the angle α with respect to a plane P3 in an end view, seeFIG. 3. It is the first section 46 of the minor edge 44 that forms theminor cutting edge 56.

Attention is now drawn to FIG. 7, showing the cutting insert 10 inaccordance with the present invention, in which the major side surfacecomprises a primary relief surface 76 adjacent the major cutting edge 54and a secondary relief surface 78 adjacent the primary relief surface76. This arrangement gives more flexibility in the design of the majorcutting edge 54 and is particularly important when designing the majorcutting edge 54 to mill a true 90° shoulder in a workpiece. The primaryrelief surface 76 can have a constant relief angle along the majorcutting edge 54, or a variable relief angle along the major cutting edge54.

Attention is now drawn to FIG. 8, showing a milling cutter 80 with anaxis of rotation R, having a cutter body 82 provided with a plurality ofinsert pockets 84. In each insert pocket 84 a cutting insert 10 inaccordance with the present invention is clamped by means of a clampingscrew (not shown). The axial rake angle will generally be in the rangeof 5° to 20°. As can be seen, each cutting insert is seated so thatthere will be a clearance between a workpiece (not shown) and thecutting insert's minor side surface 16 adjacent the milling cutter'sface 86. The structure of the insert pocket 84 is shown in detail inFIG. 9. The insert pocket 84 comprises adjacent side and rear walls 88,90 generally transverse to a base 92. The rear wall 90 is generallyconvex and the side wall 88 is provided with an axial location surface94 for abutting a given minor side surface 16 of the cutting insert 10at an axial abutment region 96. The rear wall 90 is provided with twotangential location surfaces, a upper tangential location surface 98,adjacent the pocket side wall 88 and a lower tangential location surface100 adjacent the milling cutter's face 86. The two tangential locationsurfaces 98, 100 project outwardly from the rear wall 90 and are locatedon either side of a central region 102 of the rear wall 90, which iscorrespondingly recessed relative to the tangential location surfaces98, 100. The upper tangential location surface 98 abuts an uppertangential abutment surface 104 located on the projecting abutmentsurface 30 of the cutting insert 10. The lower tangential locationsurface 100 abuts a lower tangential abutment surface 106 located on theprojecting abutment surface 30. Clearly, the terms “lower” and “upper”used here with respect to the projecting abutment surface 30 are usedonly when the cutting insert 10 is mounted in the milling cutter 80, andwith respect to the orientation shown in FIGS. 8 and 9. Similarly, withrespect to FIGS. 8 and 9, the axial abutment region 96 is located on aforward region 108 of a radially outer minor side sub-surface 110, theforward region being distal the rear wall of the insert pocket 90. Ascan be seen in FIG. 3, the two tangential abutment surfaces 104, 106 oneach projecting abutment surface 30 are located on opposite sides of theminor plane. As can be seen in FIG. 2, each minor side sub-surface 70 isprovided with one axial abutment region 96 adjacent a lowered corner 26.The base 92 of the insert pocket 84 is provided with a threaded bore 112for receiving a clamping screw in order to secure the cutting insert 10in the insert pocket 84. When the cutting insert 10 is secured in theinsert pocket 84, a radially inner major side surface 20 will abut thebase 92 of the insert pocket 84. Preferably, the major side surfaces 18of the cutting insert 10 are ground. Further preferably, the minor sidesub-surfaces 70 are ground. With these surfaces ground, good positioningof the cutting insert 10 in the insert pocket 84 is ensured.

Attention is now directed to FIGS. 10 to 12C showing a cutting insert10′ in accordance with a second embodiment of the present invention. Thecutting insert 10′ in accordance with the second embodiment is almostidentical to the cutting insert 10 in accordance with the firstembodiment. The main difference between the two cutting inserts is inthe shape of the projecting abutment member 28, 28′. As can be seen fromcomparing FIGS. 4 and 11, in both embodiments the projecting abutmentmembers 28, 28′ are concave in shape in a side view of the cuttinginsert 10, 10′, that is, each projecting abutment surface 30, 30′ lieson a concave surface S which is generally V-shaped in form in a sideview of the cutting insert 10, 10′. The difference between the twoprojecting abutment members 28, 28′ being in their shape in an end view.Like the projecting abutment member 28 of the cutting insert 10 inaccordance with the first embodiment, the projecting abutment member 28′of the cutting insert 10′ in accordance with the second embodiment has aprojecting abutment surface 30′ comprising three generally flatportions, two outer flat portions 32′ with an inner flat portion 34′therebetween. However, unlike the cutting insert 10 in accordance withthe first embodiment, the shape of the projecting abutment member 28′ inan end view of the cutting insert 10′ in accordance with the secondembodiment is not straight. As can be seen in FIG. 10, in an end view ofthe cutting insert 10′ each of the two outer flat portions 32′ has amedian line L1, L2 that is parallel to, but offset from, the major planeP2′. One median line L1 being offset to one side of the major plane P2′and the other median line L2 being offset to the other side of the majorplane P2′, with the inner flat portion 34′ being transverse to the majorplane P2′. Clearly then, in an end view of the cutting insert 10′, themedian lines L1, L2 of the two flat outer portions 32′ are parallel,non-adjacent, and spaced apart from each other. In other words, themedian lines L1, L2 of the two flat outer portions 32′ are parallel, donot overlap and do not lie on a common straight line. As a consequenceof this structure, the distance between the chip deflector 64′ and theadjacent major cutting edge 54′ remains constant along each outer flatportion 32′. This is advantageous in regions where the chip deflector64′ is high above the adjacent major cutting edge 54′ as shown on theright hand side in FIG. 12A.

As already stated, the cutting inserts 10, 10′ in accordance with thefirst and second embodiments are almost identical. In particular, beingtangential inserts each cutting insert 10, 10′ has a first majordimension D1, measured between the end surfaces 12, 12′ that is greaterthan a minor dimension D2 measured between the major side surfaces 18,18′. A second major dimension D3, measured between the minor surfaces16, 16′ is also greater than the minor dimension D2.

The cutting insert 10′ in accordance with the second embodiment isclamped in the milling cutter 80 in a similar way to which the cuttinginsert 10 in accordance with the first embodiment is clamped in themilling cutter 80. That is, the upper tangential location surface 98 ofthe insert pocket 84 abuts an upper tangential abutment surface 104′located on the projecting abutment surface 30′ of the cutting insert 10′and the lower tangential location surface 100 of the insert pocket 84abuts a lower tangential abutment surface 106′ located on the projectingabutment surface 30′. In both the first and second embodiments the uppertangential abutment surface 104, 104′ and the lower tangential abutmentsurface 106, 106′ are generally flush with the projecting abutmentsurface 30, 30′.

As can be seen in FIG. 10, in an end view of the cutting insert 10′ inaccordance with the second embodiment, the projecting abutment member28′ has an elongated, or stretched out, “S-shape”. However, as describedabove, the cutting insert 10′ in accordance with the second embodimentis clamped in the milling cutter 80 in a similar way to which thecutting insert 10 in accordance with the first embodiment is clamped inthe milling cutter 80. Clearly, other variations in the shape of theprojecting abutment member 28 are acceptable in accordance with thepresent invention, provided that in a side view, as in FIGS. 4 and 11,the projecting abutment members 28, 28′ are concave. This, is due tofact that the projecting abutment members 28, 28′ are designed to reducethe disturbance caused to the development of the chips during a millingoperation, and the rear wall 90 of the insert pocket 84 is designedcorrespondingly convex with two protruding abutment members 104, 106,104′, 106′ in order to support the concave projecting abutment surface30, 30′.

Attention is now directed to FIGS. 13 to 16C showing a cutting insert10″ in accordance with a third embodiment of the present invention. Thecutting insert 10″ in accordance with the third embodiment is almostidentical to the cutting inserts 10, 10″ in accordance with the firstand second embodiments. The difference between the cutting insert 10″ inaccordance with the third embodiment and the cutting inserts 10, 10′ inaccordance with the first and second embodiments is in the structure ofthe projecting abutment member. In accordance with the third embodiment,each end surface 12″ of the cutting insert 10″ is provided with twoprojecting abutment members 28″A, 28″C separated by a central recessedregion 28″B. Each projecting abutment member 28″A, 28″C has a projectingabutment surface 30A, 30C, wherein in a side view of either major sidesurface 18″ of the cutting insert 10″ the projecting abutment surfaces30A, 30C at each end surface 12″ lie on a concave surface S which isgenerally V-shaped in form.

The two projecting abutment members 28″A, 28″C are located on oppositesides of the minor plane P1 of the cutting insert 10″. As seen in FIG.15, a major portion of one of the projecting abutment members 28″A islocated on one side of the major plane P2 of the cutting insert 10″,whereas a major portion of the other one of the projecting abutmentmembers 28″C is located on the other side of the major plane P2.

The cutting insert 10″ in accordance with the third embodiment isclamped in the milling cutter 80 in a similar way to which the cuttinginserts 10, 10′ in accordance with the first and second embodiments areclamped in the milling cutter 80. That is, the upper tangential locationsurface 98 of the insert pocket 84 abuts an upper tangential abutmentsurface 104″ located on one of the projecting abutment surfaces 30A ofthe cutting insert 10″ and the lower tangential location surface 100 ofthe insert pocket 84 abuts a lower tangential abutment surface 106″located on the other one of the projecting abutment surfaces 30C. Theupper and lower tangential abutment surfaces 104″, 106″ are generallyflush with their respective projecting abutment surfaces 30A, 30C.

Although the present invention has been described to a certain degree ofparticularity, it should be understood that various alterations andmodifications could be made without departing from the scope of theinvention as hereinafter claimed.

1. A tangential cutting insert comprising: two identical opposing end surfaces, each end surface having four corners including two lowered corners and two raised corners, the lowered corners being closer to a median plane M than the raised corners, each end surface being provided with at least one abutment member having an abutment surface; a peripheral side surface extending between the two opposing end surfaces and comprising two identical opposing major side surfaces and two identical opposing minor side surfaces; and a peripheral edge formed at the intersection of each end surface and the peripheral side surface, at least two sections of each peripheral edge constituting cutting edges, wherein in a side view of either major side surface, the abutment surface lies on a concave surface.
 2. The cutting insert according to claim 1, wherein each minor side surface merges with an adjacent major side surface at a corner side surface, wherein each corner side surface extends between a given raised corner of one of the two opposing end surfaces and a given lowered corner of the other of one of the two opposing end surfaces.
 3. The cutting insert according to claim 1 wherein a first major dimension D1, measured between the end surfaces, is greater than a minor dimension D2 measured between the major side surfaces.
 4. The cutting insert according to claim 3, wherein a second major dimension D3, measured between the minor side surfaces, is greater than the minor dimension D2.
 5. The cutting insert according to claim 1, wherein each cutting edge comprises a major cutting edge, a minor cutting edge and a corner cutting edge, therebetween.
 6. The cutting insert according to claim 5, wherein each corner cutting edge is associated with a given raised corner.
 7. The cutting insert according to claim 5, wherein major, corner, and minor cutting edges are formed at the intersection of the major, corner and minor side surfaces respectively, with an adjacent end surface.
 8. The cutting insert according to claim 7, wherein each major cutting edge extends along substantially the whole length of an associated major edge.
 9. The cutting insert according to claim 7, wherein each minor cutting edge extends along at least half of the length of an associated minor edge.
 10. The cutting insert according to claim 1, wherein in an end view of the cutting insert the at least one abutment member has an elongated S-shape.
 11. The cutting insert according to claim 1, wherein each end surface is provided with two abutment members.
 12. The cutting insert according to claim 1, wherein in a side view of either major side surface, the abutment surface is generally V-shaped.
 13. The cutting insert according to claim 1, wherein the abutment surface comprises three flat portions, two outer flat portions with an inner flat portion therebetween, each outer flat portion extending from a respective short edge to the inner flat portion.
 14. The cutting insert according to claim 13, wherein in an end view of the cutting insert two median lines L1, L2 are defined, one for each outer flat portion, the median lines L1, L2 do not overlap and do not lie on a common straight line.
 15. The cutting insert according to claim 14, wherein the two median lines L1, L2 are parallel.
 16. The cutting insert according to claim 14, wherein the two median lines L1, L2 are parallel to the major side surfaces.
 17. The tangential cutting insert according to claim 1, wherein: the two identical opposing end surfaces have 180° rotational symmetry about a first axis Al passing therethrough, the two identical opposing major side surfaces have 180° rotational symmetry about a second axis A2 passing therethrough, the second axis A2 being perpendicular to the first axis A1, and a minor plane P1 is defined by the first axis A1 and the second axis A2; the two identical opposing minor side surfaces have 180° rotational symmetry about a third axis A3 passing therethrough, the third axis A3 being perpendicular to the first axis A1 and the second axis A2, and a major plane P2 is defined by the first axis A1 and the third axis A3; the median plane M is defined by the second axis A2 and the third axis A3; and the at least one abutment member comprises a projecting abutment surface.
 18. The cutting insert according to claim 17, wherein in an end-view of the cutting insert the at least one abutment surface is generally rectangular in shape having two parallel long edges extending between two short edges, the long edges making an angle of β with the major plane P2.
 19. The cutting insert according to claim 18, wherein β=2°.
 20. The cutting insert according to claim 17, wherein each end surface is provided with two abutment members located on opposite sides of the minor plane P1.
 21. The cutting insert according to claim 20, wherein a major portion of a first of the two abutment members is located on a first side of the major plane P2 and a major portion of a second of the two abutment members is located on a second side of the major plane P2.
 22. The cutting insert according to claim 17, wherein each minor side surface is divided into two minor side sub-surfaces by the major plane P2 along a join where the major plane P2 intersects the minor side surface, each minor side sub-surface extending away from the join at an angle α with respect to a plane passing through the join and parallel to the minor plane P1.
 23. The cutting insert according to claim 17, further comprising an insert through bore extending between the major side surfaces and having a bore axis B coinciding with the second axis A2.
 24. A milling cutter comprising: at least one cutting insert in accordance with claim 1; and a cutter body having at least one insert pocket in which the at least one cutting insert is retained, the at least one insert pocket comprising adjacent side and rear walls generally transverse to a base, the rear wall being generally convex; the side wall being provided with an axial location surface that abuts a given minor side surface of the at least one cutting insert at a given axial abutment region; the rear wall being provided with two tangential location surfaces, located on either side of a central region of the rear wall, a first of the two tangential location surfaces abuts a first tangential abutment surface located on the at least one cutting insert, a second of the two tangential location surfaces abuts a second tangential abutment surface located on the at least one cutting insert.
 25. The milling cutter according to claim 24, wherein the given axial abutment region is located on a forward region of a radially outer minor side sub-surface, the forward region being distal the rear wall of the insert pocket.
 26. The milling cutter according to claim 24, wherein the lower and upper tangential abutment surfaces are located on opposite sides of the minor plane P1.
 27. The milling cutter according to claim 24, wherein each end surface of the at least one cutting insert is provided with an abutment member and the first and second tangential abutment surfaces are located on the abutment member.
 28. The milling cutter according to claim 24, wherein each end surface of the at least one cutting insert is provided with two abutment members and the first tangential abutment surface is located on one of the two abutment members, and the second tangential abutment surface is located on the other one of the abutment members.
 29. A tangential cutting insert comprising: two identical opposing end surfaces, each end surface having four corners including two lowered corners and two raised corners, the lowered corners being closer to a median plane M than the raised corners, each end surface being provided with two abutment members separated by a central recessed region, each abutment member having an abutment surface; a peripheral side surface extending between the two opposing end surfaces and comprising two identical opposing major side surfaces and two identical opposing minor side surfaces; and a peripheral edge formed at the intersection of each end surface and the peripheral side surface, at least two sections of each peripheral edge constituting cutting edges, wherein in a side view of either major side surface, the abutment surfaces of each abutment member of a given end surface lie on a concave surface.
 30. The tangential cutting insert according to claim 29, wherein the concave surface is generally V-shaped in form. 